This research project involves the use of bi-functional cross-linking compounds to react with human hemoglobin A. These chemicals can cross-link the hemoglobin molecule intramolecularly, resulting in cross-linked hemoglobins with altered functional properties. We are interested to locate the cross-linking sites within the hemoglobin molecule and to study the functional properties of cross-linked hemoglobins as a function of several factors, such as cross-linker length, hydrophobicity, bulkiness and aromaticity. In this research we synthesize cross-linking compounds, purify proteins and peptides, and perform enzymatic digestion. Several techniques are used in this research, for example, chromatographic techniques are used to isolate and purify proteins and peptides; NMR spectroscopy is used to characterize cross-linking compounds; and Matrix Assisted Laser Desorption/Ionization Time-of-Flight mass spectrometry (MALDI-MS) is used for analysis of emzymatic digests in order to identify cross-linking sites in cross-linked hemoglobins. Cross-linked hemoglobins are potentially useful as blood substitute or short-term resuscitation fluid for keeping transplant organs alive.